The proposed studies will embrace 2 areas of steroid hormone research - metabolism and mechanisms of action. The former will concentrate on human breast cancer. We have shown that of 10 breast tumor homogenates incubated with 3H-androstenedione, one produced glucuronides of androsterone and its metabolites (10 percent). We intend to continue these studies using 3H-androsterone as substrate to see whether the extent of glucuronidation could be related to histopathology or other properties of the tumor. Also related to steroid conjugation is our finding that human breast cyst fluid contains concentration of estriol-3-sulfate about one hundred times greater than that found in blood. Studies using iv-administered 3H-estriol-3-sulfate and other estriol conjugates will be tested as potential sources of the estriol-3-sulfate concentrated in cyst fluid. The studies on hormone action will use the mouse as the test animal. We have discovered a new estrogen-responsive hydrolase activity in the mouse uterus. The enzyme is quantitated by its ability to cleave t-boc-Ala-Ala-Pro-Ala-AMC (AMC equals 4-methyl-7-aminocoumarin). Partial purification of the enzyme has been effected. We aim to purify it further and study its substrate specificity. Further investigations will center on subcellular distribution, a search for a possible endogenous substrate, hormoral specificity of induction and its relationship to estrogen action.